The Frank–Read source is a dislocation segment anchored between two obstacles. When external stress is applied, the segment bends and, upon reaching a critical stress level, generates a closed dislocation loop. This loop then moves away from the obstacles, allowing the source to generate successive loops. The initiation stress of the Frank–Read source defines the crystal’s elastic limit—the maximum stress the material can withstand without permanent deformation. This chapter focuses on analyzing the influence of the process zone on the functionality of the Frank–Read source (Korzhenevskii 1986).